Widening of the popliteal hiatus on magnetic resonance imaging leads to recurrent subluxation of the lateral meniscus

Abstract

Purpose This study was undertaken to elucidate the clinical significance of widening of the popliteal hiatus on magnetic resonance imaging (MRI), and to document the clinical results and technical aspects of arthroscopic repair of this finding. Methods Included are 82 knees after arthroscopic surgery, divided according to arthroscopic diagnosis into group A, hypermobility of lateral meniscus, 8 knees; group B, tear of the anterior horn of the lateral meniscus, 32 knees; and group C, no abnormality of the lateral meniscus, 36 knees with medial meniscal tears and 6 with other conditions. Popliteal hiatus diameter was measured and the popliteal hiatus/lateral tibial plateau (LTP) ratio was calculated on preoperative sagittal and coronal MRI. At arthroscopy, the widened popliteal hiatus in group A was tightened anteriorly by outside-in or all-inside suture and posteriorly with all-inside suture. Outcomes were evaluated with MRI, Lysholm, Tegner and VAS scores. ResultsThe preoperative diameter of the popliteal hiatus and the popliteal hiatus/LTP ratio were significantly larger in group A than in groups B and C (p < 0.05) on both views. Threshold popliteal hiatus/LTP values of 0.16 and 0.18 on the sagittal and coronal views demonstrated diagnostic discrimination, and these values were significantly reduced after arthroscopy in Group A. Lysholm and Tegner scores were improved after tightening of the popliteal hiatus, while VAS scores reduced (all p < 0.05). Conclusion Widening of the popliteal hiatus on MRI may lead to recurrent subluxation of the lateral meniscus. Arthroscopic anterior and posterior tightening of the popliteal hiatus was a safe and effective treatment. Level of evidence II.

Preoperative Magnetic Resonance Imaging as a Diagnostic Aid for Hypermobile Lateral Meniscus

“…Since some studies have reported that the widening of the popliteal hiatus on the MRI leads to a hypermobile lateral meniscus, the opening of the hiatus was also added as an item of evaluation in the current study [ 11 , 16 ]. On proton density-weighted sagittal MRI, Type 1 was defined as no clear high-signal hiatus; Type 2 was defined as a clear high-signal hiatus with a maximum width of 1 mm or less; and Type 3 was defined as a clear high-signal hiatus with a maximum width of 1 mm or more ( Figure 2 ).…”

“…Once a definitive diagnosis is made, a meniscus suture can be used to treat the condition without symptoms in most cases [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ]. The hypermobile lateral meniscus is difficult to diagnose using imaging because there is no tear or morphological abnormality of the meniscus itself and it must be diagnosed based on clinical findings alone [ 10 , 11 ]. Although good results can be achieved if the disease is correctly diagnosed, many orthopedic surgeons find it difficult to diagnose; therefore, many patients affected by their symptoms may not receive appropriate treatment.…”

“…These structures can be visualized with an arthroscope [ 10 , 14 ]. Since these PMFs are the primary restraints to anterior displacement of the posterolateral corner of the lateral meniscus at 90 degrees of flexion of the knee joint, when these fibers tear or stretch out for some reason, it is thought to cause hypermobile lateral meniscus [ 10 , 11 ]. It has been reported that such important fibers can also be depicted in the sagittal view of magnetic resonance imaging (MRI) [ 1 , 10 , 11 , 15 ].…”

“…Since these PMFs are the primary restraints to anterior displacement of the posterolateral corner of the lateral meniscus at 90 degrees of flexion of the knee joint, when these fibers tear or stretch out for some reason, it is thought to cause hypermobile lateral meniscus [ 10 , 11 ]. It has been reported that such important fibers can also be depicted in the sagittal view of magnetic resonance imaging (MRI) [ 1 , 10 , 11 , 15 ]. Although there is a study which stated that there is a high incidence of a widening popliteal hiatus as a result of injury to the sPMF and iPMF in patients with hypermobile lateral meniscus [ 11 ], there are no reports so far on the diagnostic accuracy of evaluating PMFs by MRI.…”

“…It has been reported that such important fibers can also be depicted in the sagittal view of magnetic resonance imaging (MRI) [ 1 , 10 , 11 , 15 ]. Although there is a study which stated that there is a high incidence of a widening popliteal hiatus as a result of injury to the sPMF and iPMF in patients with hypermobile lateral meniscus [ 11 ], there are no reports so far on the diagnostic accuracy of evaluating PMFs by MRI. Therefore, the purpose of this study is to clarify the diagnostic accuracy of MRI for hypermobile lateral meniscus.…”